It's true, IBS can be caused by a lot of things. I had one mild attack of diverticulitis induced by months of taking antibiotics and NSAIDS. I'm convinced of that linkage between the two. After that first mild attack I had some really intense and painful attacks with fever for three days twice. The analogy I read was those attacks are like a bomb going off in your intestines. It takes a long time for them to heal afterwards.
NSAIDS can be great medicines for acute inflammation but you just should not take them long term. You have to protect your gut lining, stomach, kidneys etc. and the good bugs that live in your gut.
Probiotics for the most part have never done anything for me with one notable exception and that's the "probiotic" substance Florastor. Florastor is a little different because it is a yeast not a bacteria. I take it occasionally and it helps a lot. I highly recommend it to anyone here with gut issues.
Do whatever you can to get off NSAIDS though and don't take antibiotics unless it's absolutely necessary.
I don't believe being in a vasectomized state causes IBS. Stress, anxiety, and medications for inflammation and pain however can tear up your gut. Most guys with post vasectomy chronic pain from nerve entrapment, engorgement of and sensitivity in their epis have tons of stress, pain, anxiety and are prescribed those medications by the wheelbarrow. Be smart about taking them.